1. Field of the Invention
The present invention relates to a recording tape cartridge which rotatably accommodates a reel on which a recording tape such as a magnetic tape or the like is wound.
2. Description of the Related Art
A recording tape such as a magnetic tape is used as an external recording medium for a computer or the like, and a so-called 1-reel recording tape cartridge is employed which rotatably accommodates a single reel of a recording tape. Advantageously, this type of recording tape cartridge requires only a small storage space and yet is capable of recording a large amount of information.
Such a recording tape cartridge includes a lock mechanism, which prevents a reel from being rotated when the recording tape cartridge is not used (for example, see Japanese Patent Application Laid-Open (JP-A) No. 63-251983). The recording tape cartridge including such a lock mechanism will be described below with reference to FIG. 10. In a recording tape cartridge 200 shown in FIG. 10, a single reel 204 is accommodated in the case 202. The case 202 has a gear opening 206 formed in a central portion of a bottom panel 202A and a rotation regulating rib 208 which is formed in such a manner as to project downward from the top panel 202B of the case 202.
The reel 204 has a reel hub 210, which has a bottomed cylindrical shape including a bottom and an outer periphery on which a recording tape is wound. A reel gear 214 which can be engaged with a drive gear 212A formed on a rotating shaft 212 of a drive device is circularly formed on the lower surface of a bottom portion 210A of the reel hub 210. Meanwhile, an engagement gear 216 is circularly formed on the upper surface of the bottom portion 210A. A through hole 218 is formed in a portion corresponding to the axial center of the bottom portion 210A. An annular reel plate 219 of a magnetic material is fixed between the reel gear 214 and the through hole 218 on the lower surface of the bottom portion 210A.
A disk-like braking member (pushed member) 220 having a lower surface on which an annular braking gear 220A, which can be meshed with the engagement gear 216, is formed is inserted into the reel hub 210. The rotation regulating rib 208 of the case 202 is inserted into an engagement projection 222 extending from the upper surface of the braking member 220, so that the braking member 220 cannot be rotated with reference to the case 202 and can be vertically moved with reference to the case 202. In addition, a pivot portion 223 formed projecting from a portion corresponding to the axial center of the lower surface of the braking member 220 intrudes into the through hole 218 of the reel hub 210 to face the gear opening 206.
A compression coil spring 224 is interposed between the top panel 202B of the case 202 and the braking member 220. Usually, the braking member 220 is downwardly biased by a biasing force of the compression coil spring 224 to cause the braking gear 220A to be meshed with the engagement gear 216. In this manner, when not in use, the recording tape cartridge 200 is set in a rotation lock state in which the reel 204 is prevented from being rotated with reference to the case 202. The reel 204 exposes the reel gear 214 from the gear opening 206 while being pressed against the bottom panel 202A of the case 202 by the biasing force of the spring 224.
On the other hand, when the recording tape cartridge 200 is loaded into the drive device, with the meshing operation between the drive gear 212A and the reel gear 214, a release portion 212B formed to project from a portion corresponding to the axial center of the rotating shaft 212 is brought into contact with the pivot portion 223 to press the pivot portion 223. In this manner, the braking member 220 is pushed up against the biasing force of the compression coil spring 224 to release the meshing state between the braking gear 220A and the engagement gear 216.
The drive gear 212A is completely meshed with the reel gear 214, and the reel plate 219 is attracted by the magnetic force of a magnet 212C of the rotating shaft 212. In this state, when the rotating shaft 212 rotates about its axis, the reel 204 is rotated together with the rotating shaft 212. At this time, the braking member 220 cannot rotate with reference to the case 202, so that the pivot portion 223 and the release portion 212B are disposed in sliding contact with each other while being pressed against each other by the biasing force of the compression coil spring 224. In order to reduce the sliding contact resistance, the pivot portion 223 of the braking member 220 is formed by a resin material, and the release portion 212B on the drive device side is also formed from a resin material. Further, the distal end of the pivot portion 223 is tapered to reduce the contact area.
A configuration in which a release member is interposed between the braking member 220 and the rotating shaft 212 is known in the art (for example, see Japanese Patent No. 3,187,022). Parts of this configuration different from those of the recording tape cartridge 200 will be described below with reference to FIGS. 11 and 12.
A recording tape cartridge 250 shown in FIG. 11 includes a release member 252 formed of a resin material which is interposed between the bottom portion 210A of the reel hub 210 and the braking member 220. The release member 252, as shown in FIG. 12, is formed in the shape of a substantially equilateral triangle when viewed from the upper side and includes leg portions 254 formed to project from respective apex portions downward. The leg portions 254 intrude into through holes 256 formed in the bottom portion 210A in place of the through hole 218 to face the gear opening 206. The through holes 256 are formed to extend through a portion where the reel gear 214 is formed on the bottom portion 210A.
A plurality of engagement projections 258 are provided on the upper surface of the bottom portion 210A in place of the engagement gear 216. The engagement projections 258 are arranged at equal intervals along a predetermined circumference to avoid the apex portions of the release member 252. Gear teeth 258A which can be meshed with the braking gear 220A are formed on the upper ends of the engagement projections 258. A sliding contact projection 260 is formed to project from the axial center portion of the upper surface of the release member 252. The sliding contact projection 260 can be always disposed in contact with a generally spherical pivot portion 262 arranged on the braking member 220 in place of the pivot portion 223. Both the sliding contact projection 260 and the pivot portion 262 consist of a resin material, and the pivot portion 262 is formed to have a spherical shape, so that the sliding contact projection 260 and the pivot portion 262 are substantially in point contact with each other.
In the recording tape cartridge 250, when the cartridge is not in use, the braking gear 220A of the braking member 220 is meshed with the gear teeth 258A of the reel 204 by the biasing force of the compression coil spring 224 to prevent the reel 204 from being rotated with reference to the case 202. In this state, the release member 252 is brought into contact with the braking member 220 at the sliding contact projection 260, and the lower surface of the release member 252 is pressed against the bottom portion 210A. The end faces of the each leg portion 254 respectively located in the through holes 256 are on the same plane as the tooth tops of the reel gear 214.
On the other hand, when the recording tape cartridge 250 is loaded into the drive device, with an operation in which the reel gear 214 is meshed with a drive gear 212A of the rotating shaft 212 having no release portion 212B, the leg portions 254 are pressed by the drive gear 212A, and the release member 252 is pushed upward against the biasing force of the compression coil spring 224. As a result, the release member 252 pushes the braking member 220 upward while being separated from the bottom portion 210A to release the meshing state between the braking gear 220A and the gear teeth 258A. The release member 252 is designed to hold the braking member 220 at the released position by the contact of the leg portions 254 and the drive gear 212A under the condition that the meshing state between the drive gear 212A and the reel gear 214 is kept.
The reel 204 is designed to rotate in the case 202 when the rotating shaft 212 rotates. At this time, the release member 252 having the leg portions 254 intruded into the through holes 256 of the reel 204 rotate together with the reel 204. The sliding contact projection 260 and the pivot portion 262 of the braking member 220 are brought into sliding contact with each other while being pressed against each other by the biasing force of the compression coil spring.
As described above, in the recording tape cartridges 200 and 250, with the rotation of the reel 204, the pivot portion 223 of the braking member 220 is brought into sliding contact with the release portion 212B of the rotating shaft 212 or into sliding contact with the sliding contact projection 260 of the release member 252. For this reason, with the rotation of the reel 204 (release portion 212B or the release member 252), the braking member 220 supported by the compression coil spring 224 may be subjected to self-excited vibration.
The rotating speed of the reel 204 is expected to be made higher to cope with the demand for an increase in recording capacity or the like. With the high-speed rotation, it is feared that abrasion or melting of the resin material occurs at the sliding contact portions which are brought into sliding contact with each other while supporting the biasing force of the compression coil spring 224. When the state or the shape of the sliding contact surfaces are changed by the abrasion or the like, the self-excited vibration of the braking member 220 occurs more easily. Such self-excited vibration causes the biasing force of the compression coil spring 224 to vary. The varying biasing force is transmitted to the case and the reel to make the travelling state of the recording tape unstable.
In a structure including the release member 252, a configuration for reducing abrasion of the sliding contact portion between the braking member 220 and the release member 252 has been proposed (for example, see JP-A No. 11-250618). The configuration will be described with reference to FIG. 13. A curved-surface recess 264 is formed in the lower surface of the axial center portion of the braking member 220 in place of the pivot portion 262, and a pivot portion 266 which projects in a spherical shape is formed on the upper surface of the axial center of the release member 252 in place of the sliding contact projection 260. An annular projection 268 is formed around the pivot portion 266. At least one of the braking member 220 and the release member 252 consists of a low-friction, low-abrasion material. With the rotation of the reel 204, the curved-surface recess 264 and the pivot portion 266 are brought into sliding contact with each other in a point contact state, and the lower surface of the braking member 220 and the annular projection 268 are brought into sliding contact with each other in a surface contact state. In this manner, the braking member 220 and the release member 252 are brought into sliding contact with each other in a low-friction, low-abrasion state to reduce the abrasion of the sliding contact portion.
However, with such a configuration, it is difficult to completely prevent the abrasion which causes self-excited vibration to easily occur in the braking member 220 as described above.
Furthermore, the problem of the self-excited vibration may generally arise not only in a lock mechanism, which locks rotation of the reel in a nonuse state but also in a portion which is elastically supported and brought into sliding contact with a rotating portion as the reel rotates. For example, in a professional-use two-reel recording tape cartridge (tape cassette) used in a broadcasting station or the like, reels and reel holders which support the reels in a case are brought into sliding contact with each other with rotation of the reels (for example, see JP-A No. 2003-45143).
More specifically, as shown in FIGS. 14 and 15, a recording tape cartridge 270 rotatably accommodates two reels 274 in a case 272. Pivot portions 277 are formed on the upper surfaces of hubs 276 of each reel 274, respectively. Meanwhile, reel holders 280 are supported by a top panel 272A of the case 272 in correspondence to the two reels 274 via center caps 278, respectively, such that the reel holders 280 cannot rotate and can be vertically moved. The reel holders 280 are always in contact with the pivot portions 277 of the corresponding reels 274 while being biased downward by compression coil springs 282 of the corresponding reels 274. In this manner, each reel 274 is swingably supported with reference to the case 272.
In the recording tape cartridge 270, when the reels 274 rotates, the pivot portions 277 and the reel holders 280 are brought into sliding contact with each other while being pressed against each other by a biasing force of the compression coil springs 282. For this reason, in the recording tape cartridge 270, self-excited vibration of the reel holders 280 becomes a problem.
As will be appreciated from the above discussion, in the various conventional recording tape cartridges, no consideration has been paid to the problem of self-excited vibration of a member such as a braking member of a lock mechanism or a reel holder which is elastically supported with reference to a case and brought into sliding contact with a reel with rotation of the reel or a member rotating together with the reel, nor to means for solving this problem.